Well perforating firing means



United States 2,883,932 WELL PERFORATING FIRING MEANS ApplicationSeptember 2, 1955, Serial No. 532,248

10 Claims. (Cl. 102-20) This invention relates to well perforatingfiring means and particularly to switch actuating means for firing awell perforating assembly adapted to be run through well tubing to befired after emergence from the lower end of such tubing.

In the completion of wells drilled by the rotary method, it has longbeen the practice to perforate casing set in the well adjacent theproducing formation for the purpose of providing ingress to the wellfrom said formation. Such perforating formerly was done before the wellwas capped and while the heavy drilling mud was within the casing, andafter perforating, the well was completed for production by removing themud, running tubing into the well and capping same. More recently,however, the practice of running in the tubing, afi'ixing the well headequipment, and replacing the drilling mud with clean fluid, all prior toperforating, has gained considerable popularity in the field, and inthis method the perforating assemblies used must be adapted to belowered through the tubing until, upon emergence therefrom in thevicinity of the oil-bearing formation, the perforating can beaccomplished.

Equipment for perforating wells completed in the aforementioned mannerhas now been devised and a particularly effective type of such apparatusis that wherein the assembly is arranged so that during the lowering ofsame through the tubing the perforating units are in vertical alignmentwith the axis of the tubing, but upon emergence of the assembly from thelower end of the tubing, said units are permitted to pivot to ahorizontal firing position. Such apparatus is disclosed in Patent No.2,543,814 of W. H. Thompson et al. dated March 6, 1951, and entitledMeans andMethod of Tilting Explosive Charges in Wells. An improvementupon the Thompson et al. patent, which patent does not provide for aretraction of the apparatus after emergence from the bottom of thetubing, resides in an application for United States Letters Patent filedFebruary 19, 1954, by Blake M. Caldwell and Joe P. Wier, Serial Number411,- 349, entitled Tilting Charge Well Perforating Assembly. A furtherimprovement upon such apparatus resides in an application for UnitedStates Letters Patent filed October 8, 1954 by Blake M. Caldwell andHarrold D. Owen, Serial Number 461,236 entitled Well PerforatingAssembly. It is with improvements in the apparatus disclosed in thelatter application that the instant invention is particularly concerned.

In such apparatus there is provided a firing head from which issuspended an elongated carrier, pivotally carrying shaped charges, theshaped charges being resiliently urged to horizontal position, but byinterlock means normally being held in axial disposition with respect tothe carrier. An explosive release means, such as a squib, abuts a detenton the bottom shaped charge and upon atent firing of the squib thebottom shaped charge is permitted to pivot to horizontal position,releasing the others so that they too may assume horizontal, or firing,position. Control means are provided in such apparatus whereby theshaped charges may not be fired in the event they are prevented as bywell obstructions from attaining the described firing position.

As shown in the aforesaid application, Serial Number 461,236, suchcontrol means comprises a release arm interlocked with the uppermostshaped charge, which release arm, upon the pivoting of said charge,throws an arming switch to which it is connected through a plungerelement. Thus after the apparatus is lowered into the well, theexplosive squib may be exploded from the surface by means of suitableelectrical circuitry, whereupon the shaped charges and release arm pivotto a horizontal firing position. In this respect it may be noted thatthe position need not be horizontal, but may be at a predetermined anglefrom the vertical. Pivoting of the shaped charges and release arm causesthe plunger to actuate the arming switch, activating a suitable circuit,which enables a detonating fuse to be fired, which in turn fires theshaped charges.

The instant invention is concerned specifically with improvements in thenature of the interconnecting plunger between release arm and armingswitch. In the aforedescribed apparatus, said plunger is positivelyconnected both to switch and to release arm, which release arm in turnis interlocked with the uppermost shaped charge. Moreover, the bottomarea of the plunger is effectively subjected to well pressure, whereasthe upper area of the plunger is sealed from such well pressure.Consequently, under suitable pressure conditions it is quite possiblethat upon explosion of the squib and release of the interlock, therelease arm could travel faster than adjacent shaped charges, due tofluid pressure on the outside of the plunger, whereby to cause firing ofthe shaped charges before the uppermost charges have been enabled toreach optimum firing position, and it is the principal object of thisinvention to provide a means whereby Well pressure cannot have thiseffect.

Additionally, it is to be noted that in the prior structure a releasearm is provided, whereas it would be more desirable to provide a shapedcharge itself, thus obtaining an additional perforation. Since, however,in the prior structure the plunger must be positively connected to therelease arm, replacement of such release arm by a shaped charge wouldrequire special construction and attendant expense. It is the furtherpurpose of this invention to provide a plunger arrangement whereby it isas feasible to use a shaped charge immediately adjacent the plunger asit is to use a non-firing release arm.

These and other objects and features and advantages of the presentinvention will be apparent from a consideration of the followingspecification taken in conjunction with the accompanying drawings inwhich:

Figure 1 shows a longitudinal sectional view of the perforating assemblyincorporating the instant invention, wherein the shaped charges are invertical disposition, and

Figure 2 shows the same view with the said shaped charges pivoted tohorizontal firing position.

In its general aspect, the invention comprises a firing head 10supported by a conductor cable, not shown, which is suspended in thewell from the surface, the well cas-,

ing 11 having tubing 12 suspended therein. Carried by the firing head 10is an elongated carrier 14, through which passes a; detonating. fuse 16detonated by the firing head. Said detonatingfuse passes adjacent shapedcharges 18, which charges are pivotally mounted within the carrier andare resiliently urged to horizontal posi-' tion, being fired by thedetonating fuse. Said charges are, however, by means such as the detents20 held interlocked in axial disposition with respect to the carrier. Arelease means, which could be solenoid or other electrioally operatedstop means, but which is shown here as the explosive cartridgeor-squib22, is electrically connected through a suitable conductor to an armingswitch 26 and'abuts the detent 2021 ofthe bottom shaped charge. Uponfiring of the squib, the bottom shaped charge is permitted toresiliently pivot to horizontal position. Pivoting of the bottom shapedcharge releases the next shaped charge for similar resilient pivotalmovement to horizontal position, and the process is repeated to permiteachcharge to assume firing disposition.

Additionally, control means are provided whereby the shaped' cha'rgesmay notbe'fir'ed from the surface in the event they are prevented,- asby well obstructions, from reaching a proper firing position. Thus aplunger 30 is connected-to the switch 26 and abuts the uppermost oftheshaped-charges 18. Upon horizontal pivoting of the shaped charges,the plunger-'30 is moved upwardly, throwing the arming switch 26' andthereby permitting a firing ofthe det'onating fuse and consequtnely theshaped charges.

-It is with the nature of the plunger arrangement that this invention isparticularly concerned, and in essence said invention resides in thearrangemet whereby the plunger is exposed at either end to wellpressures, whereby differential areasexposed to hydraulic pressure mayserve to prevent premature firing of the shaped charges, and may enablethe convenient use of an additional shaped charge rather than a releasearm in the perforating apparatu's I Detailed description of the generalperforating assembly isset forth in the aforesaid application, SerialNumber 461,236, and it is believed that the general description of saidassembly set forth above suffices, but for the arming switch controlmeans. In this regard a chamber 32 is provided Within the firing head10, which chamber houses the arming switch 26, which switch comprises acommon double pole, double throw switch actuated by the plunger 30, itbeing suflicient to say as previously set out that such switch whenthrown actuates the circuitry, which enables the firing of the shapedcharges 18 after pivotal movement of said shaped charges.

The plunger 30 is slidable in bores 34 and 36 of the firing head, whichfiring head is provided with counterbores 38 and 40 to slidably receivepiston elements 42 and 44 extending from the plunger 30. An adapter 46which serves as a support means for the entire assemblage' and which isconnected as 'by" screws or otherwis'to' the firing head 10, and whichadditionally delines with the firing head a chamber 48, is ported asat"50, s'o that well pressure may exist within said chamber' 48 againstthe piston 42. Sealing rings 52 and 54 seal the counterbores 38 and 40,respectively.

The plunger 30 is provided with a collar 56 and retaining pin 58, saidcollar abutting against the actuating arm 60 of the arming switch 26. Anabutment plate 62- extends from said arming switch and a compressionspring 64 is interposed between s'aid'plate and the actuating arm 60,whereby to urge said arm and consequently the plunger 30 to a downwardposition, in which position of course the arming switch 26 does notpermit the firing of the shaped charges 18. The lower end 66 of thepiston extension 44 of the plunger 30 merely abuts the uppermost of theshaped charges 18.

His thus seen that since both ends of the piston extensions 'of theplunger 30 are exposed to well pressures, the force of the well pressureapplied to the bottom of the plunger does not'move the plunger upwardlyand cause inadvertent or premature arming of the switch 26. Indeed, bysuitable design-of the-cross-sectional areas of upper and lower pistons,the resultant force on the said plunger may be adjusted to bedownwardly, i.e., the cross-sectional area of the piston 42 may belarger than the cross-sectional area of the piston 44. On the otherhand, because of the large pressures involved, it is most desirable thatthe cross-sectional area of the bottom piston 44 be very slightly largerthan that of the upper piston 42, large enough so that the resultantforce is in an upward direction but is insufiicient to overcome theeffect of the spring 64 and the friction in the system. This enables thewell fluid to as'sist'the uppermost shaped charge in moving the switchto armed position. It is, of course, undersirable that thecross-sectional area specifications be such that a resultant upwardforce exists sufficient to overcome spring and friction.

Additionally, it' isseen that" no particular intercounecting meansisrequired between the bottom of the plunger 30 and the uppermost shapedcharge 18, it only being necessary that the shaped charge meet said endin its upward pivot to firing position. Consequently, the same shapedcharges can be used in the assembly as uppermost shaped charges as thoseused therebelow, and special design of 'uppermost sh'aped charge isunnecessary. I

While there has been described what'isat present considered a'preferredembodiment of the present invention, it will be apparent to thoseskilled in the art that various modifications and changes maybe madewithout departing from the essence of the invention, and particularlythat the invention herein presented is adapted to various types andkinds of tools other'than well perforating assemblies. It is intended tocover herein all such modifications and changes as come within'the truescope and spirit of the appended claims. I

I claim: n

1. In a well perforating assembly having an arming switch adapted toactuate a firing circuit for shaped charges pivotally mounted in saidassembly the combination of: a firing head having a sealed chambertherein and mounting said switch in said chamber and a plunger slidablymounted within said firing head and operably connecting said switch andsaid shaped charges to close said switch upon pivoting of said shapedcharges, said plunger having each of its extremities exposed to wellfluid pressure and being resiliently biased by forces including theresultant hydrostatic force acting on the exposed extremities of saidplunger to maintain said switch open prior to pivoting of said shapedcharges.

2. In a well perforating'assembly' having an arming switch adapted toclose a firing circuit for a shaped charge pivotally mounted in saidassembly the combination of: a firing head h'a'ving'a sealed chambertherein and being adjacent said shaped-charge, said firing head mountingsaid switch in saidfchambe'r, and a plunger slidably mounted withins'a'idfiring'head and operably connecting said switch and said shapedcharge to close said switch upon pivoting of said 'shaped charge, saidplunger having each of its extremities exposed to well fluid pressuresand being resiliently biased by forces including the resultanthydrostatic 'force acting on the exposed extremities of said plu'ngertornaintain said switch open prior to pivoting of said shaped charges.

3. In a well perforating assembly having an arming switch adapted toclosea firing circuitfor a shaped charge pivotally mounted in saidassembly the combination of: a firing head having asealed chambertherein and being adjacent said shaped charge, said firing head mountingsaid'switch in said chamber; a plunger slidably mounted within saidfiring head and operably connecting said switch and saidshaped chargesto close said switch upon pivoting of 'said shaped charge and themovement of said plunger towards s'aidswitch, said plunger having eachof its extremities exposed to well fluid pressures; and resilient meansurging said plunger towards said shaped charge and maintaining saidswitch open prior to pivoting of said shaped charge, the exposedcross-sectional area of the plunger extremity adjacent said shapedcharge being larger than the exposed cross-sectional area of said otherplunger extremity to hydrostatically bias said plunger toward saidswitch to assist in closing said switch upon pivoting of said shapedcharge.

4. In a well perforating assembly having an arming switch adapted toclose a firing circuit for a shaped charge pivotally mounted in saidassembly the combination of a firing head having a sealed chambertherein and being adjacent said shaped charge, said firing head mountingsaid switch in said chamber; and a plunger slidably mounted within saidfiring head connected to said switch and abutting said shaped charge toclose said switch upon pivoting of said shaped charge towards saidswitch, said plunger having each of its extremities exposed to wellfluid pressures and being resiliently biased by forces including theresultant hydrostatic force acting on the exposed extremities of saidplunger to maintain said switch open prior to pivoting of said shapedcharges.

5. In a well perforating assembly having an arming switch adapted toclose a firing circuit for a shaped charge pivotally mounted in saidassembly the combination of: a firing head having a sealed chambertherein and being adjacent said shaped charge, said firing head mountingsaid switch in said chamber; a plunger slidably mounted within saidfiring head connected to said switch and abutting said shaped charge toclose said switch upon pivoting of said shaped charge towards saidswitch, said plunger having each of its extremities exposed to wellfluid pressures; and resilient means urging said plunger towards saidshaped charge and maintaining said switch open prior to pivoting of saidshaped charge toward said switch, the exposed cross-sectional area ofthe plunger extremity adjacent said shaped charge being larger than theexposed cross-sectional area of said other plunger extremity tohydrostatically bias said plunger toward said switch to assist inclosing said switch upon pivoting of said shaped charge.

6. In a well perforating assembly having an arming switch adapted toclose a firing circuit for a shaped charge pivotally mounted in saidassembly the combination of: a firing head having a sealed chambertherein and being adjacent said shaped charge, said firing head mountingsaid switch in said chamber; and a plunger slidably mounted within saidfiring head and operably connecting said switch and said shaped chargeto close said switch upon pivoting of said shaped charge and themovement of said plunger towards said switch, said plunger having eachof its extremities exposed to well fluid pressures, the exposedcross-sectional area of the plunger extremity adjacent said shapedcharge being smaller than the said exposed cross-sectional area of saidother plunger extremity to hydrostatically bias said plunger away fromsaid switch and maintaining said switch open prior to pivoting of saidshaped charge.

7. In a well perforating assembly having an arming switch adapted to arma firing circuit for a perforating unit pivotally mounted in saidassembly the combination of: a firing head having walls providing anenclosed chamber, said walls having a pair of openings therethrough, thearming switch being mounted within the chamber; a plunger slidablyreceived in the openings of said walls and extending through the chamberand having each of its extremities exposed to well fluid pressure, saidplunger being operably connected to the switch to close the switch uponsliding movement of said plunger, said plunger being constructed andarranged for engagement by the perforating unit to be slidingly moved toclose the switch upon pivotal movement of the perforating unit and beingresiliently biased by forces including the resultant hydrostatic forceacting on the exposed extremities of 6 said plunger to maintain saidswitch open prior to pivoting of said shaped charges; and means slidablysealing said plunger in the openings of said walls.

8. In a well perforating assembly having an arming switch adapted to arma firing circuit for a perforating unit pivotally mounted in saidassembly the combination of: a firing head having walls providing anenclosed chamber, said walls having a pair of opposed openingstherethrough, the arming switch being mounted within the chamber; aplunger slidably received in the opposed openings of said walls andextending through the chamber and having each of its extremities exposedto well fluid pressure, said plunger being operably connected to theswitch to close the switch upon sliding movement of said plunger, saidplunger being constructed and arranged for engagement by the perforatingunit to 'be slidingly moved to close the switch upon pivotal movement ofthe perforating unit and being resiliently biased by forces includingthe resultant hydrostatic force acting on the exposed extremities ofsaid plunger to maintain said switch open prior to pivoting of saidshaped charges; and means slidably sealing said plunger in the openingsof said walls.

9. In a well perforating assembly having an arming switch adapted to arma firing circuit for a perforating unit pivotally mounted in saidassembly the combination of: a firing head having walls providing anenclosed chamber, said walls having a pair of opposed openingstherethrough, the arming switch being mounted within the chamber; aplunger slidably received in the opposed openings of said walls andextending through the chamber and having each of its extremities exposedto well fluid pressure, the exposed cross-sectional area of one of theextremities of said plunger being different from the exposedcross-sectional area of the other of the extremities of said plunger,said plunger being operably connected to the switch to close the switchupon sliding movement of said plunger, said plunger being constructedand arranged for engagement by the perforating unit to be slidinglymoved to close the switch upon pivotal movement of the perforating unitand being resiliently biased by forces including the resultanthydrostatic force acting on the exposed extremities of said plunger tomaintain said switch open prior to pivoting of said shaped charges; andmeans slidably sealing said plunger in the openings of said walls.

10. A well perforating assembly comprising in combination: a firing headproviding a sealed chamber therein; an elongated carrier mounted on saidfiring head; a well perforating unit exposed to well fluid and pivotallymounted on said carrier in axial disposition with respect thereto;resilient means urging said perforating unit to pivot from said axialdisposition to lateral firing disposition; retaining means releasablyholding said perforating unit in said axial disposition; means foroperating said retaining means to release said perforating unit formovement from said axial disposition to said firing disposition underurgence of said resilient means; means for firing said perforating unitincluding an arming switch mounted in the chamber of said firing head,said arming switch having an armed position and a disarmed position; aplunger slidably mounted in said firing head and having a portionextending through said chamber; pistons carried by the ends of saidplunger and slidably received in cylinders formed in said firing head,the outer extremities of said pistons being exposed to well fluidpressure, said plunger being operatively connected to said switch tomove said switch between said armed and said disarmed positions uponsliding movement of said plunger and pistons in said firing head; secondresilient means urging said plunger and pistons to a position disarmingsaid switch; said plunger and pistons 'being freely slidable betweenpositions to disarm and to arm said switch when said perforating unit isin said axial disposition, the crosssectional areas of said pistons thatare exposed to Well fluid pressure beinggsuchv that theresultant-hydrostatic RefrencsCited in -thafile-ofithispatent forceacting-on said pistons is insufficient to-move said STATESJPATENTSplnnger and pistons frgm said 'switph disarmingrposi tion against thebias of saidisegonflresilient means and fric- .Ti g- 31, 1943 tionforms; one of' said pistns being positioned tQ-bC I 3 AP engaged by saidiperff rat ing unit assaidperforating unit 2,644,519 Kan dy July 7, 1953pivots from saidi axial disposition" to said firin'g:. disposi h .w ticnto slide s'aidiplungel and'pist ns-to-move said switch FOREIGN PATENTSfroms'aid disarm'ed to said arm'ed disposition. 475,873 Ganada in. Aug.7, '19'51-

